Removal of heavy metals from leaching effluents of sewage sludge via supported liquid membranes.

Heavy metal content of sewage sludge is one of the factors preventing its agricultural use. Leaching processes have been used to solubilize heavy metals and thus reduce metal content of the sludge through chemical or biological routes. Subsequent to leaching processes, metal removal from the supernatant is attractive in terms of decreasing metal content of the effluent and recovering metals. This paper investigates application of supported liquid membrane (SLM) technology for metal removal from leaching effluents. SLM system was first optimized using synthetic metal mixtures. Optimized system was then used for the anaerobic bioleaching and chemical leaching effluents and metal removal efficiencies of 27.1 ± 1.3% and 46.0 ± 4.3% were obtained, respectively. Considering integrated leaching and membrane separation processes, metal removal efficiencies obtained in this study are valuable as it will decrease the metal content of sludge and increase the metal solubilization during leaching process. Future integration of metal leaching and removal technologies would make it possible to develop a sustainable system involving heavy metal removal from sewage sludge, land application of the sludge with a low metal content, and metal recovery.